Bizjak

If you need to use a center support, do not limit yourself to using complete circle curtain hangers. You could due or make a hanger similar in shape to a question mark. Then support the center of the span from the bottom. You could also think of this approach like one of the under supported closet hanger bars. The one draw back is the hooks could jump off the track, or catch on the support if pulled out and over at the same time. You can search curtain hooks in google to see examples